The invention relates to a spinneret bundle for producing fibers from its polymer melt.
A generic spinneret bundle is described DE 10 2006 017 212. This generic spinneret bundle is used for producing nonwovens, in which the fibers extruded through an array of a plurality of nozzle bores are extracted by means of airflow. In this respect, a nozzle package can be used for melt blowing a plurality of fibers. The polymer melt is supplied through a melt inlet provided on an upper distributing plate of the nozzle package. The melt inlet opens into a distributing chamber which, in turn, opens into a feed channel of a nozzle plate. The distributing chamber within the distributing plate and the feed channel within the nozzle plate extend along a row of nozzle bores that are connected with the feed channel. A filter element and a perforated plate are provided between the distributing chamber and the feed channel. Furthermore, a displacer is provided in the feed channel to achieve the lowest possible melt residence times within the nozzle package, thus generating relatively small flow areas and consequently higher flow rates.
However, such displacers generally have the disadvantage that, depending on their shape, they form more or less distinctive dead zones, which do not receive continuous melt flow. As a result, it is not possible to adequately eliminate the different melt residence times. A further disadvantage that may occur, especially with polymer melts, is that higher shearing energy is generated by the displacer due to reduced flow rates, which results in a temperature increase and a change of the viscosity of the melt. Such occurrences can be local so that irregularities could occur through the nozzle bores over the length of the nozzle package when extruding melt.
To achieve a uniform distribution of polymer melt over an extended length of the nozzle package, WO 2007/131714 discloses a spinneret bundle in which multiple distributing chambers are arranged one next to another within the distributing plate and which are connected with the feed channel in the nozzle plate through a perforated plate having a plurality of hole groups. At the same time, each distributing chamber is associated with one of the hole groups on the perforated plate, wherein the distributing chambers are supplied with a polymer melt via separate melt inlets.
Consequently, these known nozzle packages are suitable to be used in the production of nonwovens with large production widths of >5 m. Because of the plurality of melt inlets and the plurality of spinning pumps required for that purpose, such a nozzle package is too costly for small production widths.